decisions/2026-10-05-pm-agent-issue-to-pr.md

@@ -90,6 +90,26 @@ All offline, in the pinned toolbox (`./infra/devcontainer/dev.sh run`), never on
      kustomization, because the kustomization's comment named it by filename. Correctly
      refused: the distance between a filename in a comment and a line under `resources:` is
      one careless edit. The comment now points at it in prose.
+- **`infra/agent/probe-validation.sh` → 17 refusals, 0 failures.** A new, committed
+  negative-path probe for `pm-worker`'s input guards — the things that stand between an
+  injected environment variable and a clone from the wrong host or a push to the wrong ref.
+  Each case asserts a non-zero exit AND the specific message, so a guard that stopped firing
+  cannot pass by failing somewhere else. It refuses: an argument on the pinned command;
+  `main`, a wrong prefix, `feat/x;id`, `../../etc/passwd`, too-short slugs, and a branch equal
+  to the base; a redirected git host, a real-and-reachable wrong one (`github.com` — the
+  egress policy permits tcp/443, so this one is genuinely reachable), and the right host with
+  a smuggled path; a malformed owner or repository; an unknown mode; a non-numeric and a zero
+  issue number; and each missing credential. `build-image.sh` also runs it inside the built
+  image, where the interpreter is the one that will run in the cluster.
+- **Writing that probe corrected an overclaim in the code.** The `PM_BRANCH != "main"` guard
+  is UNREACHABLE while the pattern check above it holds (`main` has no `feat|fix|docs|chore/`
+  prefix), so the comment claiming it as the defence against pushing to main was wrong about
+  which line does the work. It is kept — as an assertion that does not depend on the regex
+  being right — and the comment now says so.
+- **Two more defects found by self-review of the unattended paths, both fixed:** the worker's
+  `EXIT` trap ended in a failing test, which under `set -e` can replace the script's real exit
+  code with that failure; and a provenance *log line* read a file through a redirect that
+  `set -o pipefail` would have turned into a dead worker if the file were absent.
 - **A self-review of the trigger found and fixed one real defect** before any of this ran:
   `last_activity()` compared RFC 3339 timestamp STRINGS to find the newest comment, which is
   only correct while every offset Gitea returns is identical — and the failure mode is the

docs/plans/pm-agent-issue-to-pr.md

@@ -215,7 +215,10 @@ holds a git write token and can author code. So:
 under the pinned CLI (the first run was 27/28 and caught a real defect: the volume rule
 denied a valid `emptyDir: {}`); `check-jsonschema` on the changed ServiceDefinition; the
 canonical render reproduces `apps/wave-0/gitea.yaml` with the new policy in it; `bash -n`
-and `ast.parse` on the two entrypoints. **`./ci/gate.sh` → exit 3 (UNDETERMINED), with
+and `ast.parse` on the two entrypoints; `PM_SELFTEST=1 pm-dispatch` → 26 assertions, 0
+failures; `infra/agent/probe-validation.sh` → **17 refusals, 0 failures** against
+`pm-worker`'s input guards, including the three that matter most (a redirected git host, a
+reachable-but-wrong one, and `main` as the branch). **`./ci/gate.sh` → exit 3 (UNDETERMINED), with
 `gitea-settings` the one stage that did not run** — no `SETTINGS_API_TOKEN` on this
 workstation — and every other stage green, `spec-immutability` included. rc 3 is not a pass.
 The gate also refused an earlier revision of this change twice, both times correctly; see

infra/agent/build-image.sh

@@ -134,6 +134,21 @@ if [ "${VERIFY}" -eq 1 ]; then
       echo "--- no Anthropic API key is baked into the image (it would outrank the subscription token) ---"
       [ -z "${ANTHROPIC_API_KEY:-}${ANTHROPIC_AUTH_TOKEN:-}" ] && echo "    confirmed: neither is set"
     '
+  # The worker's input guards, exercised in the image, with the interpreter and the script
+  # that will actually run in the cluster. The probe is mounted read-only rather than baked
+  # in: it is a build-time check, not something a worker Job has any business carrying.
+  log "Probing pm-worker's input validation inside the image"
+  "${ENGINE}" run --rm \
+    --user 65532:65532 \
+    --read-only \
+    --tmpfs /workspace:rw,mode=1777 \
+    --tmpfs /tmp:rw,mode=1777 \
+    --network none \
+    --volume "${HERE}/probe-validation.sh:/probe-validation.sh:ro,Z" \
+    --entrypoint "" \
+    "${IMAGE_REF}" \
+    /bin/bash /probe-validation.sh
+
   log "Image verified"
 fi
 

infra/agent/pm-worker

@@ -73,8 +73,15 @@ esac
 [[ "${PM_BRANCH}" =~ ^(feat|fix|docs|chore)/[a-z0-9][a-z0-9-]{2,48}$ ]] \
   || die "PM_BRANCH '${PM_BRANCH}' does not match ^(feat|fix|docs|chore)/[a-z0-9][a-z0-9-]{2,48}$"
 
-# NEVER the default branch. A worker that could be handed PM_BRANCH=main would push to main
-# on its first commit, which CLAUDE.md §1 forbids in the strongest terms it has.
+# NEVER the default branch. A worker handed PM_BRANCH=main would push to main on its first
+# commit, which CLAUDE.md §1 forbids in the strongest terms it has.
+#
+# The base-branch check is the one that can fire on its own: a slug that satisfies the
+# pattern above can still equal PM_BASE_BRANCH if someone sets that to a feature branch.
+# The literal `main` check below is UNREACHABLE while the pattern holds — `main` has no
+# `feat|fix|docs|chore/` prefix — and is kept deliberately anyway, as an assertion that does
+# not depend on that regex being right. If the pattern is ever loosened, this still holds.
+# infra/agent/probe-validation.sh exercises both, and records which message each produces.
 [ "${PM_BRANCH}" != "${PM_BASE_BRANCH}" ] || die "PM_BRANCH must not be the base branch"
 [ "${PM_BRANCH}" != "main" ] || die "refusing to work on 'main' (CLAUDE.md §1)"
 
@@ -115,7 +122,13 @@ OUT=/workspace/out
 mkdir -p "$SRC" "$OUT" "$TMPDIR" "${CLAUDE_CONFIG_DIR:-/workspace/.claude}"
 
 log "assignment: issue #${ISSUE} · mode ${PM_TASK_MODE} · branch ${PM_BRANCH} · model ${MODEL}"
-log "toolchain: $(cat /etc/agent-runner-versions 2>/dev/null | tr '\n' ' ')"
+# Guarded with a readability test rather than a redirect plus `2>/dev/null`: redirections are
+# applied left to right, so a failing `< file` is reported by the shell BEFORE stderr is
+# silenced. And guarded at all because `set -o pipefail` + `set -e` would otherwise let a
+# missing provenance file (this script run outside the image) kill the worker on a LOG LINE.
+VERSIONS=""
+[ -r /etc/agent-runner-versions ] && VERSIONS="$(tr '\n' ' ' < /etc/agent-runner-versions)"
+log "toolchain: ${VERSIONS:-(no provenance file; not the agent-runner image?)}"
 
 # --- 2. the Gitea API, and git credentials that never touch disk in a URL ----
 # WHY GIT_ASKPASS AND NOT A CREDENTIAL IN THE REMOTE URL (or ~/.git-credentials): a token
@@ -214,7 +227,11 @@ report_failure() {
   } > "${OUT}/failure.md"
   post_issue_comment "${OUT}/failure.md"
 }
-trap 'rc=$?; [ "$rc" -ne 0 ] && report_failure "an unhandled error (exit ${rc}); see the worker log"' EXIT
+# An `if`, not `test && report`: the EXIT trap's own exit status matters under `set -e`, and
+# a trailing failed test in it can replace the script's real exit code with that failure. The
+# `if` form always leaves the trap returning 0, so the status the script exits with is the one
+# it meant.
+trap 'rc=$?; if [ "$rc" -ne 0 ]; then report_failure "an unhandled error (exit ${rc}); see the worker log"; fi' EXIT
 
 # --- 3. clone and put the branch under our feet ------------------------------
 log "cloning ${PM_GITEA_OWNER}/${PM_GITEA_REPO} from ${PM_GITEA_URL}"

infra/agent/probe-validation.sh

@@ -0,0 +1,120 @@
+#!/usr/bin/env bash
+###############################################################################
+# infra/agent/probe-validation.sh — prove pm-worker REFUSES hostile input.
+#
+#   ./probe-validation.sh          # from anywhere; needs only bash
+#
+# WHY THIS EXISTS. pm-worker's `command` is pinned by admission with no args, so everything a
+# caller could influence arrives in the ENVIRONMENT — and the guards at the top of that
+# script are what stand between an injected variable and a clone from the wrong host, a push
+# to the wrong ref, or a session with the wrong credential. Guards that nothing exercises are
+# a claim, not a control. Each case below asserts BOTH a non-zero exit AND the specific
+# message, because a check that only grepped stderr would pass a build where the guard had
+# stopped rejecting and something else had started failing instead.
+#
+# Every case must die BEFORE the script reaches any network call: the probe runs with a
+# scrubbed environment and fake credentials, and if a guard ever stopped firing, the case
+# would fail here rather than by really cloning something.
+#
+# Run offline, no cluster, no Gitea, no model. infra/agent/build-image.sh runs it inside the
+# built image as well, where the interpreter and the script are the ones that will actually
+# run in the cluster.
+###############################################################################
+set -uo pipefail
+
+HERE="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+WORKER="${PM_WORKER_PATH:-${HERE}/pm-worker}"
+[ -r "$WORKER" ] || { echo "cannot read ${WORKER}" >&2; exit 2; }
+
+# A complete, VALID assignment. Each case below overrides exactly one thing, so a failure
+# names the guard rather than a pile of missing variables.
+BASE=(
+  PM_TASK_MODE=implement
+  PM_ISSUE_NUMBER=42
+  PM_BRANCH=feat/some-real-slug
+  PM_BASE_BRANCH=main
+  PM_GITEA_URL=http://gitea.gitea.svc.cluster.local:3000
+  PM_GITEA_OWNER=Home-Network
+  PM_GITEA_REPO=home-network-k3s-impl
+  PM_GITEA_USER=pm-agent
+  GITEA_TOKEN=not-a-real-token
+  CLAUDE_CODE_OAUTH_TOKEN=not-a-real-token
+)
+
+PASS=0
+FAIL=0
+
+# `env -i` so nothing from the invoking shell leaks in and accidentally satisfies a guard.
+refuses() {
+  local label="$1" want="$2"; shift 2
+  local out rc=0
+  out="$(env -i PATH="$PATH" HOME=/tmp "${BASE[@]}" "$@" bash "$WORKER" 2>&1)" || rc=$?
+  if [ "$rc" -eq 0 ]; then
+    printf '  FAIL %s — exited 0; it should have been refused\n' "$label"
+    FAIL=$((FAIL + 1))
+    return
+  fi
+  if printf '%s' "$out" | grep -qF "$want"; then
+    printf '  ok   %s (exit %s)\n' "$label" "$rc"
+    PASS=$((PASS + 1))
+  else
+    printf '  FAIL %s — refused (exit %s) but not for the expected reason %q:\n' "$label" "$rc" "$want"
+    printf '%s\n' "$out" | tail -3 | sed 's/^/         /'
+    FAIL=$((FAIL + 1))
+  fi
+}
+
+echo "pm-worker input-validation probe ($WORKER)"
+
+# An argument on a pinned command is caller-supplied code. There is no argument surface.
+out="$(env -i PATH="$PATH" HOME=/tmp "${BASE[@]}" bash "$WORKER" --layer l2 2>&1)" || rc=$?
+if printf '%s' "$out" | grep -qF "takes no arguments"; then
+  echo "  ok   arguments are refused (exit ${rc:-?})"; PASS=$((PASS + 1))
+else
+  echo "  FAIL arguments are refused — got: $(printf '%s' "$out" | tail -1)"; FAIL=$((FAIL + 1))
+fi
+
+# --- the ref it may create and push ---------------------------------------
+refuses "branch 'main' (CLAUDE.md §1)"          "does not match"  PM_BRANCH=main
+refuses "branch with a wrong prefix"            "does not match"  PM_BRANCH=feature/x
+refuses "branch with a shell metacharacter"     "does not match"  'PM_BRANCH=feat/x;id'
+refuses "branch with path traversal"            "does not match"  'PM_BRANCH=../../etc/passwd'
+refuses "branch too short for the slug rule"    "does not match"  PM_BRANCH=fix/ab
+refuses "branch equal to the base branch"       "must not be the base branch" \
+        PM_BRANCH=feat/same-slug PM_BASE_BRANCH=feat/same-slug
+
+# --- where code comes FROM and goes TO -------------------------------------
+# The namespace's egress policy permits tcp/443 to the world (the model needs it), so an
+# injected host would be REACHABLE. These are the cases that matter most.
+refuses "a redirected git host"                 "is not an allowed git host" \
+        PM_GITEA_URL=https://evil.invalid
+refuses "a real, reachable, WRONG git host"     "is not an allowed git host" \
+        PM_GITEA_URL=https://github.com
+refuses "the right host on a smuggled path"     "is not an allowed git host" \
+        PM_GITEA_URL=http://gitea.gitea.svc.cluster.local:3000/../..
+refuses "a malformed owner"                     "PM_GITEA_OWNER is malformed" \
+        'PM_GITEA_OWNER=../other-org'
+refuses "a malformed repository"                "PM_GITEA_REPO is malformed" \
+        'PM_GITEA_REPO=repo;id'
+
+# --- the assignment itself -------------------------------------------------
+refuses "an unknown task mode"                  "must be 'implement' or 'revise'" \
+        PM_TASK_MODE=merge
+refuses "a non-numeric issue number"            "must be a positive integer" \
+        PM_ISSUE_NUMBER=42x
+refuses "issue number zero"                     "must be a positive integer" \
+        PM_ISSUE_NUMBER=0
+
+# --- the credentials ------------------------------------------------------
+refuses "a missing model credential"            "CLAUDE_CODE_OAUTH_TOKEN is not set" \
+        CLAUDE_CODE_OAUTH_TOKEN=
+refuses "a missing git credential"              "GITEA_TOKEN is not set" \
+        GITEA_TOKEN=
+
+echo
+if [ "$FAIL" -eq 0 ]; then
+  echo "probe OK — ${PASS} refusal(s), 0 failure(s)"
+  exit 0
+fi
+echo "probe FAILED — ${FAIL} of $((PASS + FAIL)) case(s) did not refuse as expected"
+exit 1

platform/pm-agent/README.md

@@ -151,7 +151,9 @@ nobody enumerated — on the sibling policy that was `initContainers` (measured:
 compliant `containers[0]` and a privileged init container was **admitted**, pass 3 fail 0),
 then `ephemeralContainers`, then `env`, then `envFrom`. All of them are closed here from the
 start, and `platform/kyverno/tests/pm-agent/` proves each refusal offline: **28 assertions,
-28 passing** under the pinned `kyverno` CLI.
+28 passing** under the pinned `kyverno` CLI. The worker's own input guards have their own
+offline probe — `infra/agent/probe-validation.sh`, **17 refusals** — because a guard nothing
+exercises is a claim rather than a control.
 
 > The policy is applied by `platform-config/kustomization.yaml`, and it has to be: adding a
 > ClusterPolicy only to `platform/kyverno/admission/kustomization.yaml` is a **silent